Intramolecular and Intermolecular Charge Transfer Spectroscopy in UVVIS and IR Region in Different E

来源 :The 5th Asian Photochemistry Conference(第五届亚洲光化学会议) | 被引量 : 0次 | 上传用户:Garyzhaoqi
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  An effort to explain the ground and excited state intra/intermolecular charge transfer photophysics of Pyrrole-2-Carboxyldehyde (PCL), Pyrrole-2-carboxylic acid (PCA) and its related compounds in UV-VIS and IR region has been reported here.Possible origins of dominant absorption bands have been assigned successfully with ab ignition HF and DFT calculations taking the effects of hydrogen bonds in account in the IR region and experimentally it is verified by the IR stretching and bending mode vibrations of different parts of the molecule.The possibility of transfer of hydrogen from pyrrole ring towards formyl ring in excited state indicates in the light of difference in bond length and bond angle, dipole moment, enthalpy, Gibbs free energy etc.The absorption maximum and oscillator strength computed from HF (RHF, UHF), DFT calculations for gas phase, nonpolar medium, polar medium agrees reasonably well with experimentally measured data.Quantum chemical calculations on the charge density distribution and stretching of N-H bond indicated that PCA, PCL are good candidate for intramolecular proton transfer in excited state[1,4].The absorption spectra of PCA in different solvent point the presence of intramolecularly hydrogen bonded closed conformer in the form of 280 um band.Stokes shifted fluorescence of PCA at 310 nm in hydrocarbon solvent and hydroxylic solvents have been identified to be due to anionic form of molecule.Variation of pH results enhancement or decrease of emission from ionic conformer with parallel dwindling of emission of neutral species.In hydroxylic medium inside nanocavity (cyclodextrin, micelle) the charge transferred state of the molecule affected heavily.
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